Caval Involvement of Renal Cell Carcinoma

Renal cell carcinoma; venous invasion; caval extension; surgery; prognosis in all cases (6).Immunohistochemical markers like antifactor-VIII have proven to be useful in the search of microscopic venous invasion (6, 7).Increasing the number of samples and slides per sample also improves the detection rate (6).Microvascular invasion has turned out to be an independent prognostic factor with adverse impact on disease-free survival (7, 8, 9).On the contrary and somewhat unexpectedly, caval extension as such seems not to be an independent prognostic factor, if the tumour is completely removed (4,10,11,12).Hanke and coworkers examined the surface structure of caval tumour thrombi with light-and scanning electrone microscopy and immunohistochemically by Q-band factor VIII marking (13).They found that the free floating parts of the venous thrombi were covered with endothelium and compared this phenomen to abdominal hernia covered with peritoneum.Thus microscopic venous invasion may result from different cellular mechanisms compared with macroscopic renal vein and caval extension.The speed of growth of the venous extension is not known.Many patients with caval tumour thrombus and simultaneous metastatic disease will not undergo operation and die relatively quickly of the generalized tumour burden with no documentation of the growth speed of the venous part.The upwards propagation of the thrombus and its circumferential expansion are most likely slow processes because in many patients venous collaterals have time to become wide and there is no swelling of the lower extremities.The tumour thrombus is for the most part loose from the caval wall but may invade the orifices of the renal and hepatic veins, which has to be taken into account when planning the surgery (14).The terms extension and invasion should not be mixed.In cases of true invasion of the caval wall this is also evident in microscopic examination (15).However, wall invasion seems not to depend on the level of the free thrombus (11).It is not clear how much blood circulation to the cells of the tumour thrombus comes from the renal arterial inflow, compared with possible diffusion